ES2306139T3 - INDUSTRIAL PROCEDURE FOR THE PRODUCTION OF ACETALS IN A SIMULATED MOBILE MILK REACTOR. - Google Patents

Abstract

The present invention is an industrial process for the preparation of acetals using a simulated moving bed (SMB) reactor system to accomplish the conversion of reactants (aldehyde and alcohol) and simultaneously, the separation of the reaction products (acetal and water) by selective adsorption. The SMB reactor consists of a set of interconnected columns packed with an acid solid (or mixture of acid solids: catalysts and adsorbents) effective for catalyzing the reaction between aldehydes and alcohols and for separating the reaction products by selective adsorption of at least one product. In a general embodiment, this process involves (1) feeding a mixture of aldehydes and alcohols and a desorbent which is the alcohol, to a simulated moving bed reactor; (2) reacting aldehydes and alcohols to form acetals; and (3) removing from the simulated moving bed reactor two liquid streams, a first liquid stream comprising a solution of acetal in the desorbent (raffinate), a second liquid stream comprising the water formed and the desorbent (extract).

Description

Industrial procedure for the production of acetals in a simulated mobile bed reactor.

This invention relates to a process. novel for the continuous preparation of acetals at scale industrial in a simulated mobile bed reactor (SMBR).

Background of the invention

Acetals with chemical structure R 2 -CH- (O-R 1) 2 they are oxygenated compounds produced by the reaction between a aldehyde (R2 -CHO) and an alcohol (R1 -OH) in the presence of an acid catalyst, according:

one

Traditionally, the reaction is catalyzed by carboxylic or mineral acids (US Patent 2 519 540, US 5 362 918 and US 5 527 969). The disadvantage of using soluble catalysts is which must be neutralized after the reaction and separated from the product. Therefore, heterogeneous catalysts are used as resins of ion exchange (acid type) or zeolites, which have the advantage to easily separate from the reaction product and to have a long-term (patents EP 1167 333 A2 and US 4 579 979).

Acetal synthesis is a reaction reversible. In order to obtain acceptable acetal yields,  the balance must shift in the direction of the synthesis of acetal Several methods are used to shift the balance towards Acetal formation, such as:

one.

use a large excess of one of the reagents, in general alcohol, which then it requires the removal of that excess at a stage of purification of the desired product (US Patent 5 362 918);

2.

use an organic solvent to remove water by distillation azeotropic between a solvent and water or by extraction liquid-liquid, an additional stage of separation to remove the solvent from the final product (patents US 2 519 540, US 4 579 979, US 5 362 918 and US 5 527 969);

3.

use reactive separations in order to remove products from reaction medium, the reactive distillation process being the most common (US Patent 5 362918).

The procedures described above they introduce some improvement in acetal production; but nevertheless, They also have several advantages. In the first method, the conversion of the limiting reagent increases but decreases the yield of the reaction. The second presents higher conversions but is necessary to use a solvent; consequently, the cost of starting materials and equipment. Reactive distillation does not could be applied to all systems, due to the formation of azeotropes and / or incompatible volatilities of reagents and the products. The formation of by-products is also possible.

In recent times, in addition to the Well-known applications of acetals have been considered as  diesel additives, mainly the acetaldehyde-diethylacetal. It is confirmed that the use of acetals decreases particulate emissions and NO_ {x} while maintaining or improving the cetane number and helps combustion of the final products, without diminishing the quality of the ignition (patents DE 2 911 411, DE 3 136 030, WO 2001/181 154 A1, WO 2002/026 744 A1).

Brief description of the figures

Figure 1 shows a representation schematic of the SMBR procedure of the present invention, in which are introduced both reagents (alcohol and aldehyde) in a single power supply

Figure 2 shows a second representation schematic of the SMBR procedure of the present invention, in which reagents (alcohol and aldehyde) are introduced into different supply currents.

Figure 3 shows the profiles of internal concentration in a SMBR at half a time of change in the cyclic steady state.

Summary of the invention

The purpose of the invention is to provide a alternative procedure for the manufacture of acetals, achieving 100% aldehyde conversion, without using organic solvents additional and without formation of by-products.

The acetals produced by the procedure of the present invention are used in the formulation of perfumes and aromatization of alcoholic beverages. Acetal it also finds widespread use as an intermediate product for synthesis of various industrial chemical compounds used to agricultural and pharmaceutical products (vitamins and analgesics). Particularly acetaldehyde-diethylacetal is used as a solvent and intermediate in the process in which the protection of the carboxylic groups of the aldehydes Diethylacetal is also used as a diesel additive, since it decreases particle emissions and NO_ {x}.

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Detailed description of the invention

The present invention relates to a effective and continuous procedure for the preparation of acetals that comprises the reaction of an aliphatic aldehyde simultaneously lower with a lower aliphatic alcohol in the presence of solid acid and the separation of the acetals produced from the water formed in the SMBR unit.

Acid solids, which must be simultaneously catalysts and selective adsorbents, could be acidic ion exchange resins, zeolites (Y, mordenites, ZSM, ferrierites), alumina silicates (mortmorillonites and bentonites) or hydrotalcites. Examples of acid resins are Dowex 50 (Dow Chemical), Amberlite IR 120, Amberlyst A15 and A36 (Rohm & Haas), Lewatit (Bayer). These acid solids preferably adsorb water instead of acetals. Alternatively, it is possible to use a mixture of acid solids as a catalyst and as a selective adsorbent.

Simulated mobile bed reactor technology is being applied recently for the preparation of esters to from carboxylic acids, see, for example, the patent U.S. number 6 518 454 and U.S. patent number 6 476 239. In the procedure based on the simulated moving bed, use the different affinity of the solid adsorbent to separate the products.

More precisely, the present invention addresses of the process of preparing acetals in a bed reactor simulated mobile, which comprises the reaction between alcohol and aldehyde in the presence of an acid solid (or a mixture of a solid acid catalyst and a selective adsorbent) and separation Simultaneous reaction products (acetal and water) by adsorption.

Preferably, this method comprises the following stages:

I. feed a reactive mixture (alcohol and aldehyde) and a desorbent (alcohol) to the SMBR unit, equipped with a series of columns packed with acid solid (or a mixture of acid solids);

II. make the alcohol react with the aldehyde to produce acetal and water;

III. eliminate two streams, a first liquid stream comprising an acetal solution in the desorbent (refining); a second liquid stream comprising the Water formed and desorbent (extract).

The reactor is equipped with several openings of inlet and outlet, and several valves arranged in such a way that any power supply could be introduced into any column and any output current could be removed or effluent of any column. During the operation of the SMB unit, the columns to which the currents are fed supply and from which the output currents are removed They move periodically. To achieve product separation reaction, the locations of the input and output currents they move intermittently in the direction of the flow of liquid. The intermittent movement of the opening in the liquid flow direction simulates bed countercurrent or of the beds of the solid (s), for example, of the solid catalyst

The simulated mobile bed reactor used in the present invention is a known apparatus and comprises several columns by zone; each column is packed with a solid or a solid mixture As depicted in Figure 1 and in the Figure 2, the SMB reactor normally has 4 or 5 zones.

The lower alcohol has the chemical structure next

R1 -OH,

in which R_ {1} represents a C 1 -C 8 alkyl group, linear or branched.

Preferably, the alcohol includes such a group like methyl, ethyl, propyl and butyl. Examples of these alcohols they are methanol, ethanol, propanol and butanol.

The lower aldehyde has the chemical structure next

R 2 -CHO,

in which R2 represents a C 1 -C 8 alkyl group, linear or branched.

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Preferably, the aldehyde includes a group such as methyl, ethyl, propyl and butyl. Examples of these Aldehydes are formaldehyde, acetaldehyde, propionaldehyde and butyraldehyde

Therefore, the acetal produced has the next chemical structure

R 2 -CH- (O-R 1) 2

in which R_ {1} and R2_ are the mentioned alkyl groups previously.

The process of the invention produces lower acetals (C 3 -C 24) that have preferably from 3 to 12 carbon atoms, for example formaldehyde-dimethylacetal, -diethylacetal, -dipropylacetal, -dibutylacetal; acetaldehyde dimethylacetal, diethylacetal, -dipropylacetal, -dibutylacetal; propionaldehyde dimethylacetal, diethylacetal, -dipropylacetal, -dibutylacetal; butyraldehyde dimethylacetal, diethylacetal, -dipropylacetal, -dibutyl acetal.

Acid solid catalysts are usually zeolites, alumina silicates, hydrotalcites or resins of acidic ion exchange.

The adsorbent is usually an activated carbon, molecular sieves, zeolites, alumina silicates, alumina, silicates or acidic ion exchange resins.

The simulated mobile bed reactor used in The present invention is a known apparatus and comprises 1 to 6 columns by zone; each column is packed with a solid or a solid mixture As depicted in Figure 1 and the Figure 2, the SMB reactor normally has 4 or 5 zones. He reactor is equipped with several inlet and outlet openings, and several valves arranged in a way that could introduce any supply current into any column and any outflow or effluent could be removed of any column. During the operation of the SMB unit, the columns to which the feed streams are fed and from which the output currents are removed they move periodically To achieve separation of products from reaction, the locations of the input and output streams are they move intermittently in the direction of the flow of liquid. Intermittently moving the opening in the direction of the liquid flow simulates the countercurrent of the bed or of the beds of the solid (s), for example, of the catalyst solid.

In the present invention could be introduced two streams (desorbent and one feed stream) or three currents (desorbent and two feed currents) in the SMBR unit, in which the desorbent is the same alcohol used to produce the acetal.

The first operating model considers only one supply current, as shown in the Figure 1. The supply current consists of aldehyde pure, or a mixture of alcohol and aldehyde.

In the second operating model, the two reagents are introduced into two feed streams, according to the Figure 2. Each power supply could contain one of the pure reagents: one with pure alcohol and the other with aldehyde pure; or both feed streams are mixtures of alcohol and aldehyde, one richer in alcohol and the other richest in aldehyde.

Normally, the SMBR operates at temperature from about 5 ° C to 150 ° C and at the pressure from approximately 100 kPa to 3500 kPa.

Preferably, the SMBR is maintained at a temperature from about 10 ° C to about 70 ° C

In the process of the present invention, the input / output currents periodically move from position P 'to position P, this time being called, change time

The operation of the SMBR allows the displacement of the input / output currents, or towards front or back, in a synchronous or asynchronous way, within a period of change.

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Experimental section

The simulated mobile bed reactor used in The present invention is a known apparatus (US Patent 2 985 589), which comprises several columns connected in series; every column is packaged with a solid or a mixture of solids. Sen They introduce two or three currents into the unit. One of them is the desorbent which is normally the alcohol used as a reagent for form acetal; the desorbent is used to regenerate the solid in the first zone. Reagents (alcohol and aldehyde) could be introduced into a single supply current (figure 1) or in two supply currents (figure 2). The products (acetal and water) are extracted from the simulated moving bed reactor in two liquid streams; a first liquid stream comprising a solution of acetal in the desorbent (refining), and a second liquid stream comprising the water formed and the desorbent (abstract). During the operation of the SMBR unit, the openings to which the feed streams are fed and from which the output currents are removed they move periodically in the direction of the flow of liquid. The movement intermittently of the opening in the direction of the flow of liquid simulates the countercurrent between the solid (s) and the liquid The reactor is equipped with several openings of inlet and outlet, and one rotary valve or several valves arranged in such a way that any one could be introduced power supply in any column and could be removed any output stream or effluent from any column. The position of the input / output currents defines the different areas that exist in the SMBR system, each one carrying out certain function and containing a variable number of columns

In Figure 1, zone I is comprised between the opening (D) of desorbent stream and the opening (X) of extract stream; Zone II is comprised between the opening (X) of extract stream and the opening (F) of feed stream; zone III is comprised between the opening (F) of the supply current and the opening (R) of the refining current; and zone IV is comprised between the opening (R) of refining current and the opening (Rec) of recirculation current. Reagents (alcohol and aldehyde) introduced into the feed stream (F) are converted into zones II and III. In these areas, separation of the products formed (acetal and water) is carried out; the acetal is extracted from the refining opening and water is extracted from the extract opening. Since the products are extracted from the reaction medium as they are formed, the equilibrium shifts towards the formation of products. Therefore, the conversion of the aldehyde increases to values above the thermodynamic equilibrium; being possible to achieve the complete conversion (100%). The satisfactory design of SMBR implies the correct choice of operating conditions, mainly of the period of change time and of the flow rates in each section of the unit. The appropriate choice of these parameters will guarantee the regeneration of acidic solid (or mixture of solids) that contains the adsorbed water, in zone I; the generation of desorbent contaminated with acetal in zone IV; and the complete conversion of the reagents and the separation of the products formed in the zones
II and III. The flow rates for each section are facilitated by the following expressions: Q_ {I} = Q_ {Rec} + Q_ {D};
Q_ {II} = Q_ {Q} - Q_ {X}; Q_ III = Q_ {II} + Q_ {F}; Q_ {IV} = Q_ {III} - Q_ {R} = Q_ {Rec}. The time of change, t *, is the time required to move all openings from the P 'position to the P position. This procedure for moving the openings could be performed synchronously or asynchronously.

The process of the present invention could be performed over a wide range of temperature and pressure. The temperature could vary from 5 ° C to 150 ° C; preferably, from 10 ° C to 70 ° C; and is limited by boiling points of the components at the operating pressure of the SMBR. Normally pressure is not a critical issue; unless I know use to prevent evaporation of components. Therefore the pressure range is from atmospheric pressure to 3500 kPa.

The SMBR procedure represented schematically in figure 2 it is similar to the one described above corresponding to figure 1. The main difference is that introduces an additional supply current into the system, which which leads to 5 operating zones. This allows it to be enter reagents separately into the system; one (the least adsorbed) is carried in stream F and the other (the most adsorbed) in the current F_ {2}. Alternatively, the current of F1 feed may be a richer reagent mixture in the least adsorbed reagent and the feed stream F2 It is a richer mixture in the most adsorbed reagent. He How this SMBR procedure works is similar to the previous one: the regeneration of the acid solid and the desorbent is carried out in zones I and V, respectively; and the complete conversion of reagents and the separation of the products formed occurs in Zones II, III and IV.

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Example

The procedure described herein The invention is best illustrated by the following example. Be analyzed the samples on a gas chromatograph and separated the compounds in a fused silica capillary column, using a thermal conductivity detector for peak detection. He example refers to the synthesis of acetaldehyde-diethylacetal from ethanol and acetaldehyde in a simulated mobile bed reactor, using the Amberlyst 15 acidic ion exchange resin as catalyst and as selective adsorbent. For this reaction, at temperature environment and for an initial molar ratio of 2.2 of ethanol / acetaldehyde, the equilibrium conversion is 55%.

Novasep (Vandoeuvre-dès-Nancy, France) conducted the experiments in SMBR in a pilot unit LICOSEP 12-26. Twelve columns Superformance SP were connected 230 x 26 (length x d.i., mm), by Götec Labortechnik (Mühltal, Germany), packed with Amberlyst 15 acid resin (Rohm and Haas) to the SMBR pilot unit. Each column is wrapped with shirt to ensure temperature control and shirts are connected to each other by flexible silicone tubes and to a bathroom with thermostat (Lauda). Between every two columns there is a four-opening valve operated by means of the control. When necessary, the valves allow either pumping of the feed / eluent streams into the system or either the withdrawal of the extract / refining streams. Each of the input currents (feed and eluent) and output (extract and refining) is pumped using HPLC pumps. Pump recirculation is a three-head membrane pump of positive displacement (Milton Roy, Pont St. Pierre, France) that can deliver flow rates of only 20 ml / min up to 120 ml / min The other flows (desorbent, extract, feed and refining) are controlled by the four Merck pumps - Hitachi (Merck-Hitachi models L-6000 and L-6200, Darmstadt, Germany), connected to a RS-232 computer. Flow rate maximum in desorbed current and extract pumps is 30 ml / min, while in the power supply and power pumps Refining is 10 ml / min. The maximum allowable pressure is 6 MPa. Between the twelfth and first column there is a six valve openings used to collect samples for measurements of internal concentration profile. The team has its own software of procedure control, which can carry out the following chores:

?

Change the currents of entry and exit at regular time intervals (such as assign the user) by opening and closing pneumatic valves on and off;

?

Maintain flow rates of stable and constant section as assigned;

?

Maintain suction pressure at the recirculation pump around a reference point assigned by the user (usually 1500 kPa).

Each column was packaged with Amberlyst 15, with an average particle diameter of 800 mm. Length, porosity and apparent density of the columns were 23 cm, 0.4 and 390 kg / m 3, respectively. Experiments of plotter in all columns in order to determine the number of Peclet (Pe), which allows the evaluation of the effects of axial dispersion The average value calculated for the twelve columns  in the range of flow rates used in the SMBR is Pe = 300

The feed stream was a mixture of ethanol (30%) / acetaldehyde (70%) and the desorbent was ethanol (99.5%). The flow rates were QD = 50.0 ml / min; QF = 10 ml / min; Q R = 25 ml / min; Q_ = 35 ml / min and
Q_ {Rec} = 20 ml / min. The change time was set at 3.70 minutes and three columns were used per zone (figure 1). Internal concentration profiles were achieved at half the time of change after the cyclic steady state as shown in Figure 3. It is possible to observe that acetaldehyde is converted almost completely, which means that the conversion is almost The 100%. As mentioned earlier, the products are extracted in different streams; The diethylacetal is carried in the refining stream and the water in the extract. The product obtained in a fixed bed adsorption reactor (FBAR) operating in the steady state is compared with the refining product obtained in the SMBR, in terms of weight percentage, in the following table:

2

The conversion of acetaldehyde at the exit of FBAR is 54.5%, close to the equilibrium value. For the SMBR, the Conversion is 99.7%. In addition, the refining product obtained in SMBR contains 71% diethylacetal with a purity by weight of 99.7% without ethanol (98.4% molar); while the product of the FBAR It contains 48% diethylacetal with a purity by weight of 70.8% without ethanol (37.1% molar).

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Bibliography

T. Aizawa , H. Nakamura , K. Wakabayashi , T. Kudo , H. Hasegawa , "Process for Producing Acetaldehyde Dimethylacetal", U.S. Patent No. 5,362,918 ( 1994 ).

J. Andrade , D. Arntz , G. Prescher , "Method for Preparation of Acetals", US Patent No. 4,579,979 ( 1986 ).

LW Blair , ST Perri , BK Arumugam , BD Boyd , NA Collins , DA Larkin , CW Sink , "Preparation of Esters of Carboxylic Acids", U.S. Patent No. 6,518,454 ( 2003 ).

LW Blair , EB Mackenzie , ST Perri , JR Zoeller , BK Arumugam , "Process for the preparation of Ascorbic Acid", US Patent No. 6,476,239 ( 2002 ).

K. Boennhoff , "1,1-Diethoxyethane as Diesel Fuel", German Patent No. 2 911 411 ( 1980 ).

K. Boennhoff , "Method for enhancing the ignition performance of diallcoxyalkanes used as diesel fuel, in particular 1,1-diethoxyethane", German patent number 3 136 030 ( 1983 ).

V. Boesch , JR Herguijuela , "Process and Manufacturing Equipment for Preparing Acetals and Ketals", European Patent Number 1167 333 A2 ( 2001 ).

PL Bramwyche , M. Mudgan , HM Stanley , "Manufacture of Diethyl Acetal", US Patent No. 2 519 540 ( 1950 ).

A. Golubkov , "Motor Fuel for Diesel Engines", WO Patent No. 2001/0 181 154 A1 ( 2001 ).

A. Golubkov , I. Golubkov , "Motor Fuel for Diesel, Gas-Turbine and Turbojet Engines", US Patent Number 2002/0 026 744 A1 ( 2002 ).

MM Kaufhold , MT El-Chabawi , "Process for Preparing Acetaldehyde Diethyl Acetal", US Patent No. 5 527 969 ( 1996 ).

Claims (18)

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1. Procedure for the preparation of acetals using a simulated mobile bed reactor (SMBR) system to carry out the conversion of reagents that are aldehyde and alcohol in the presence of an acid solid (or mixture of acid solids: catalysts and adsorbents) and, simultaneously, the separation of reaction products (acetal and water) by adsorption selective 2. Method according to claim 1, which It comprises the following stages:

I.

feed a reactive mixture that is alcohol and aldehyde and a desorbent (alcohol) to the SMBR unit, equipped with a series of columns packed with acid solid (or a mixture of acid solids);

II.

make the alcohol react with the aldehyde to produce acetal and water;

III.

eliminate two streams, a first liquid stream comprising an acetal solution in the desorbent (refining); a second liquid stream comprising the Water formed and desorbent (extract).

3. Method according to claims 1 or 2, in which the simulated mobile bed reactor comprises 4 or 5 zones, and each zone has several columns. 4. Method according to claims 1, 2 or 3, the alcohol used as a reagent has the chemical structure next R1 -OH, in which R_ {1} represents a C 1 -C 8 alkyl group, linear or branched. 5. Method according to claim 4, the Cited alcohol may be methanol, ethanol, propanol or butanol. 6. Method according to claims 1, 2 or 3, the aldehyde used as a reagent has the chemical structure next R2_CHO in which R2 represents a C 1 -C 8 alkyl group, linear or branched. 7. Method according to claim 6, the cited aldehyde can be formaldehyde, acetaldehyde, propionaldehyde or butyraldehyde. 8. Method according to claims 1 to 7, the acetal produced has the following chemical structure R 2 -CH- (O-R 1) 2, in which R_ {1} and R2_ are the mentioned alkyl groups previously. 9. The method according to claim 8, said acetal may be formaldehyde dimethylacetal, diethylacetal,
-dipropylacetal, -dibutylacetal; acetaldehyde dimethylacetal, diethylacetal, dipropylacetal, dibutyl acetal; propionaldehyde-dimethylacetal, -diethylacetal, -dipropylacetal, -dibutylacetal; butyraldehyde-dimethylacetal, -diethylacetal, -dipropylacetal or -dibutylacetal. 10. Method according to claims 1 to 9, the solid acid catalyst is selected from zeolites, silicates alumina, hydrotalcites or ion exchange resins acidic 11. Method according to claims 1 to 10, the adsorbent is selected from activated carbon, sieves molecular, zeolites, alumina silicates, alumina, silicates or acidic ion exchange resins. 12. Method according to claim 1, in which could introduce two currents (desorbent and one supply current) or three currents (desorbent and two supply currents) in the mobile bed reactor unit simulated, in which the desorbent is the same alcohol used to produce acetal 13. Method according to claim 12, in which the feed stream is an aldehyde stream pure, or a mixture of alcohol and aldehyde, in which only introduces a supply current into the system. 14. Method according to claim 12, in which the feed streams are two separate streams of pure reagents (alcohol and aldehyde), or two reagent mixtures, one richer in alcohol and the other richest in aldehyde, when two feed streams are used.

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15. Method according to claim 1, in which the simulated mobile bed reactor is operated at a temperature from 5ºC to 150ºC at a pressure of from 100 kPa up to 3500 kPa. 16. Method according to claim 15, in which the simulated mobile bed reactor is operated at a temperature from 5ºC to 70ºC. 17. Method according to claim 1, in that the input / output currents move periodically from position P 'to position P, this time being called, change time 18. Method according to claim 17, in that the input / output currents move, or towards front or back, in a synchronous or asynchronous way, within a period of change.